Is the prostration of forgetfulness (sujood as-sahw) obligatory for one who forgets a prostration (sajdah) in a supererogatory (nafila) prayer, and is it permissible to make it up?

The prostration of forgetfulness (Sujud Al-Sahw) is prescribed for every prayer, whether supererogatory (nafilah) or obligatory (fard). If one forgets a prostration in a supererogatory or obligatory prayer, and remembers it before beginning the recitation in the next rak'ah, they should return, perform it and what follows it, and then perform the prostration of forgetfulness. However, if they do not remember it until after they have begun the recitation in the next rak'ah, the rak'ah in which the prostration was forgotten becomes invalid, and the subsequent rak'ah takes its place. One returns to the neglected pillar as long as they have not bowed in the next rak'ah. If a long time passes, the entire prayer must be repeated from the beginning.